Out of warranty by 3 days, NT$650,000 out of pocket

You do airport runs every day, and in a year you cover several times the distance most owners do. One day you open the Tesla app and see only a few thousand kilometres left on the battery warranty. The battery feels fine. Surely there's nothing to worry about?

EBC News reported on 3 October that several taxi drivers' Model 3 Long Range cars ran into trouble soon after passing the battery warranty's 192,000 km^[1]. They say that after a software update installed as Tesla instructed, a battery fault appeared and the estimated range dropped by about 100 km^[1]. One driver, who does airport transfers, says he had the car checked at Tesla shortly before, and nothing was found^[1].

The owner says Tesla put the fault down to long-term Supercharging without slow charging to balance the voltage differences between cells^[1]. His car was 3 days and more than 1,200 km past the warranty^[1]. He says Tesla offered to pay NT$50,000, leaving him to pay the remaining NT$650,000 himself^[1]. The car still drives, but it can't use Superchargers^[1].

In short: the battery warranty is 8 years or a set distance, whichever comes first. If you drive a lot, the distance usually comes first. While you're still covered, check what needs checking and keep records.

Two numbers, and the first one reached counts

Under Tesla Taiwan's terms, the battery warranty on the Model 3 and Model Y Long Range and Performance is 8 years or 192,000 km, whichever comes first^[2][3]. Standard versions get 8 years or 160,000 km^[2][3]. During the warranty the battery keeps at least 70% of its capacity, counted from the day the car was delivered^[3].

For a hard-working car: at 60,000 km a year, 192,000 km comes after about 3 years and 2 months, long before 8 years are up. Your own car's warranty documents are what count: an older car keeps the terms in force when it was bought^[2].

Some things the battery warranty doesn't cover^[3]:

• Gradual loss: batteries slowly lose capacity with time and use, and that isn't covered.
• Changes from software updates: the car receives new features and improvements over the air, including updates that protect battery life. Noticeable changes in battery performance from these updates aren't covered.
• Damage and accidents: collisions, flooding, or the battery being opened or repaired by anyone other than Tesla.

The terms also say the estimated range doesn't fully reflect battery capacity, and that Tesla decides how capacity is measured. To get a free repair, you have to tell Tesla within the warranty period^[3]. Tesla Taiwan's extended warranty doesn't cover the high-voltage battery, and commercial vehicles can't buy it^[4].

What does "balancing the cells" mean?

A battery is many cells joined in groups, and their voltages are never exactly the same. The gap between the highest and the lowest is the voltage difference. While charging, the battery management system brings the cells' charge back into line: that's balancing. We explain how it works in "Battery health at 90%: does that mean the battery is fine?".

A 2026 study in the journal Nature Energy followed 116 electric cars in China, up to 300,000 km each^[5]. The cars balanced continuously while charging, and the voltage gap between their cells rarely went above 100 mV (millivolts)^[5]. Up to about 170,000 km their cells stayed close; after that, some cars' cells began to drift apart^[5].

But balancing evens out charge, not capacity, as researchers at the Idaho National Laboratory (INL) in the US point out^[6]. Once a cell has really weakened, no amount of balancing brings it back.

What the research says: fast charging, heat and cells

INL tested two battery packs from 2012 Nissan Leafs in the lab, at 30°C^[6]. One was charged only on AC, the other only with 50 kW DC fast charging^[6]. After the equivalent of about 80,000 km (50,000 miles), the AC pack had lost 23.1% of its capacity and the fast-charged pack 28.1%^[6].

Run the same way on single cells with tight temperature control, the gap between fast and slow charging was under 1%^[6]. The researchers put most of the packs' extra loss down to heat: uneven temperatures inside a pack make cells age at different rates, and the gap keeps widening^[6]. These packs had no active cooling, a harsher setting than a car with liquid cooling.

Cars on the road have shown milder results. Recurrent, a US company that researches EV batteries, analysed 13,000 Teslas^[7]. Cars that fast charged over 70% of the time showed no statistically significant difference in range loss from those under 30%, at least not yet^[7].

These studies describe averages and trends, not why any one car failed. Tesla's owner's manual recommends charging from a household socket or a Wall Connector when you can, and saving Superchargers for long trips^[8]. We've gathered more fast-charging research in "Does fast charging really harm the battery?" (in Chinese).

Six things to do before your warranty ends

1. Check the end date and distance: the Tesla app's specs and warranty section shows how much time and how many kilometres your car has left^[2].
2. Have Tesla check the car before it ends: report any problem while you're still covered, as the terms require^[3].
3. Keep records: screenshot any alerts and changes in range, and keep service records with dates and distances^[3]. Save the battery health figure under Controls > Service > Battery Health too^[9].
4. Charge slowly day to day where you can: Tesla's owner's manual recommends it, with Superchargers saved for long trips^[8].
5. Get an independent check, then another later: compare the cell voltage gap over time to see whether it's widening^[5]. CELLPROOF's test reads the cell voltage gap, but no test can promise a battery won't fail.
6. Look up recalls by VIN: enter your car's 17-character VIN in Tesla's VIN recall search^[10]. The terms say skipping software updates or recalls may affect the warranty^[3].

Already out of warranty?

Get a written estimate: before an appointment, Tesla runs remote diagnostics and lists an estimate in the app, and if the cost changes, no work goes ahead without your consent^[2]. Ask whether an adjustment programme applies: the terms say Tesla may, case by case, pay some or all of a repair no longer under warranty^[3]. A high-voltage battery fitted by Tesla has its own parts warranty of 4 years or 80,000 km^[2].

Compare other quotes: in October 2024, Knews reported on a commercial Model 3 Long Range with 320,000 km on it^[11]. The owner posted Tesla's quote: NT$684,577, parts and labour included^[11].

Independent workshops: out of warranty, Tesla says you can go to Tesla or a third party you trust, though Tesla isn't responsible for problems a third party causes^[2]. The Reporter quotes an industry view that fewer than 1% of Taiwan's repair shops can truly repair EVs^[12]. If you go elsewhere, ask about high-voltage training and whether the repair comes with a warranty, and get the quote in writing.

An expired warranty doesn't mean the battery will fail. In the Nature Energy study, the fleet's cells stayed close up to about 170,000 km^[5]. But once the warranty ends, repairs are on you, and if you drive a lot, that day comes sooner. This is as of 4 October 2026; terms and prices may change, so check Tesla's latest information.

The battery warranty is time or distance, whichever comes first: check what you need to while you're still covered.